Functional porous fibres

ABSTRACT

The invention relates to a method for the preparation of porous polymeric fibres comprising functionalized or active particles. By extruding a mixture of one or more dissolved polymers with particulate material a porous fibre is obtained in which the particulate material is entrapped. Extrusion of the fibre occurs under two-step phase inversion conditions. In particular the porous fibres can be used for the isolation of macromolecules such as peptides, proteins, nucleic acids or other organic compounds from complex reaction mixtures, in particular from fermentation broths. Another application is the immobilization of a catalyst in a reaction mixture.

FIELD OF THE INVENTION

The present invention relates to a method for the preparation of porouspolymeric fibres comprising functionalised or active particles, inparticular comprising particles that are still accessible and activeafter preparation, and to the porous polymeric fibres thus obtained.Also the invention relates to the use of such fibres as means ofpurification and/or isolation of a component from a (complex) mixture,like for instance fermentation broths or as catalyst in reactionmixtures. For such use preferably the porous polymeric fibres arecomprised in modules such as described hereinbelow.

BACKGROUND OF THE INVENTION

Porous polymeric matrices comprising particles have been describedbefore.

For instance in U.S. Pat. No. 6,048,457 cast porous polysulfone membranestructures comprising sorptive particles such as active carbon, (fumedor derivatised) silica or (functionalised) polystyrenedivinylbenzenebeads are described. It concerns cast-in-place structures confined inpipette tips for small scale sample preparation.

Another example is U.S. Pat. No. 5,258,149 in which a hollow fibremembrane comprising polysulfone polymer and silica is described. It isstated that silica acts as a pore former and viscosifier in membraneformation and that fibres with silica are not microporous until the bulkof the silica is removed by treatment with base. The hollow fibremembrane is immobilised by heat treatment under pressure in the presenceof polyacrylic acid. The polyacrylic acid binds to the fibre walls andacts as an affinity agent for low density lipoprotein cholesterolcomplex (LDL-C).

In U.S. Pat. No. 5,238,735 the preparation of a microporous polyolefinhollow fibre comprising synthetic resin particles is described byextruding a mixture of (co)polyolefin(s), synthetic resin particles andplasticiser, from a melt at a temperature of 230° C., into a strandwhich was cut into pellets. The resulting pellets were extruded from themelt at a temperature of 215° C. through a hollow fibre producingnozzle. In order to introduce the desired porosity the unstretchedhollow fibre is monoaxially stretched by a roll-stretching methodresulting in a molecularly oriented microporous hollow fibre.

Also in WO 00/02638 a porous polymeric matrix comprising substantiallyimmobilised material is described. Such a flexible sheet membrane (flat,pleated or rippled) has a selectively permeable skin on the outersurface. In particular the preparation of a membrane by flow casting aslurry-like blend of polyurethane and activated charcoal onto apolyester support is described. It is mentioned that the blend can alsobe extruded onto a support. Further it is also noted that the membranecan be made without an integral support, for instance by applying theblend to a drum and thereafter peeling the membrane off the surface ofthe drum. In passing it is noted that also other configurations thanflat sheet membranes can be formed such as fibres, rods and tubes.However, besides the embodiment of flow casting a membrane onto asupport none of the other suggestions are enabling disclosed.

In WO 98/34977 a porous composite product formed from at least onewater-insoluble polymer, at least one water-soluble polymer and at least20% of at least one filler material, in particular active carbon, isdescribed. The product is obtained by a melt extrusion process, using anextruder. The porosity in the product is introduced by eliminating thesoluble polymer from the extruded product. It is stated the polymericmaterial is non-fibrous and rather concerns a film of porous compositeproducts.

Thus, in the art methods are known to prepare porous polymeric materialcomprising particulate material in one step from an appropriate mixtureof starting components. Such a material is prepared by a casting processand either is limited in its three dimensional size by the housing it iscast into or is in the form of a sheet. Such casting processes are notsuitable for the preparation of fibres.

In order to prepare porous polymeric fibres comprising particulatematerial an additional process step is required to introduce the desiredporosity. After the step of preparing the fibre comprising particulatematerial either particulate material is removed form the non-porousfibre or the non-porous fibre is stretched resulting in porous fibres.Only in the latter case a microporous fibre comprising particles havinga certain (sorptive) function is obtained.

Disadvantages of the known porous polymeric fibre preparation processesare that they involve additional process steps after the formation ofthe fibre to come to a final product. It is desirable to have a moreefficient preparation process. Depending on the actual process stepsthat need to be taken to come to the final product suitable startingmaterials have to be selected with properties that can sustain theconditions of the additional process steps. Obviously such a requirementputs limitations on the polymeric material that can be used. Furthermoreit puts limitations on the type of particulate material that can becomprised in the polymeric matrix. A high degree of particle loadingwill reduce the mechanical strength of the fibre and therefore restrictthe stretching procedure. The degree of loading will be limited by theforce required to reach sufficient stretching of the matrix material. Bystretching of the particle comprising material the particulate materialcan drop out of the porous structure to be formed. In processes whichinvolve melt extrusion only particulate material that can sustaintemperatures required to melt the matrix polymer can be applied. It isnot uncommon that these temperatures are well above 200° C.

DD A 233,385 discloses a method for the preparation of porous fibres,comprising a one-step phase inversion or so-called wet-spinning process.Immediately after extrusion the fibre enters a coagulation bath.Particles are applied to maintain porosity during drying at elevatedtemperatures; the accessibility and functionality of the particles areless critical therein. It is stated that the properties and behaviour ofthe end-product are essentially determined by the chemical structure ofthe polymer used.

Drawback of a method according to DD A 233,385 is that direct spinningin a coagulation bath with less than 60 wt. % solvent results in ratherdense exterior surfaces and limited particle accessibility. However, anincrease in the amount of solvent results in difficulties of controllingthe spinning process; due to delayed demixing of the nascent fibresolidification takes too long.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a porous fibre comprisingparticulate material having a certain functionality by a process, whichcan be operated at room temperature or reigned temperatures and does notrequire additional process steps after the formation of the fibre.

A further object is to provide a method allowing the use of a variety offunctional particles that can be taken up in the polymeric matrix orsupport structure. Multiple types of particles with differentfunctionalities or particles with more than one functionality may beused.

Said functional particles should be accessible and maintain theirfunctionality once incorporated inside the matrix (support structure) ofthe porous fibre.

Surprisingly it has been found that the objects of the invention are metby a method in which a solution of one or more polymers is mixed withparticulate material. By extruding the resulting mixture a porous fibrecan be obtained in which the particulate material is entrapped.Optionally additives and/or non-solvents may be added to the polymersolution. Extrusion of the fibre occurs under phase inversionconditions.

Thus, according to the invention a method is provided for thepreparation of a polymeric matrix having particulate material entrappedin said matrix in which the polymeric matrix is porous and the particlesare well accessible and maintain their functionality after preparation,said method comprising providing a mixture of dissolved polymericmaterial and particulate material and extruding said mixture into afibre and solidify said fibre by a two-step phase inversion process.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a scanning electron micrograph (SEM) of a porous solid fibreprepared according to example 1.

FIGS. 2 and 3 arm magnifications of FIG. 1.

FIG. 4 is a scanning electron micrograph (SEM) of a porous hollow fibreprepared according to example 2.

FIG. 5 shows a SEM picture of the exterior surface of a solid PES/CERfibre prepared with a NMP/water (70/30 wt. %) mixture as first coagulantaccording to example 5.

FIG. 6 shows a SEM picture of the exterior surface of a solid PES/CERfibre prepared with a NMP/water (90/10 wt. %) mixture as first coagulantaccording to example 5.

FIG. 7 shows a SEM picture of a PES/CER fibre with a particle content of10% by weight. Macrovoids are clearly visible.

FIG. 8 shows a SEM picture of a PES/CER fibre with a particle content of75% by weight. The fibre is free of macrovoids.

DETAILED DESCRIPTION OF THE INVENTION

A method has been found for the preparation of a porous polymeric fibrehaving particulate material in said fibre. Advantageously in the step inwhich the fibre is formed the porosity in the fibre is introducedsimultaneously and thus the necessity of additional pore formingtreatments is no longer present.

An additional advantage of the method of the invention is that it doesnot influence the integrity of the particulate material during theextrusion step. The method offers the possibility to entrap particleshaving a variety of functionalities in a polymeric matrix. Heatsensitive particles that cannot be melt-extruded because of the elevatedtemperatures required to melt the matrix polymer can be incorporatedinto a porous matrix by the phase inversion process without danger ofdamaging the particle. The fibres can be processed under mildconditions.

Extrusion of the fibre occurs under phase inversion conditions. Phaseinversion, or phase separation, can be induced by: the change oftemperature of the homogeneous solution (thermal phase separation), theevaporation of solvent from a polymer solution that contains a nonvolatile non-solvent (evaporation induced phase separation), thepenetration of a non-solvent vapor (vapor induced phase separation), orimmersion of the homogeneous polymer solution in a non-solvent bath(immersion induced phase separation).

In general phase inversion extrusion processes require polymer solutionsin which the concentration of polymer is more than 12% by weight.Unexpectedly the presence of particulate material allows the use ofpolymer solutions of lower concentration. In particular it allows theuse of polymer concentrations of less 12% by weight, more particularlyof less than 10% by weight.

By the method of the invention it is possible to establish particleloaden matrices of infinite length. Obviously it is to be understoodthat instead of a particle loaden matrix of infinite length alsomatrices of very short length can be produced by the same technique.Either the infinite matrix structure is cut or crushed into small piecesafter the structure is solidified, or the polymer solution containingthe particles is extruded through an extruder such as a spinneret atshort intervals or by other means that causes droplets leaving theextruder instead of a continuous fibre.

The term fibre used herein includes hollow and solid fibres. Dependingon the type of application a suitable form of the fibre; either hollowor solid, is selected.

Also depending on the desired objectives and properties of the resultingfibres a person skilled in the art will appreciate that many differentparticles can be used. For instance when applied as a means fordetoxification or purification by removing toxic or undesired (small)organic compounds absorptive particulate material may be used such asfor instance activated carbon.

In a preferred embodiment of invention however, the porous fibres areapplied to isolate desired molecules. In particular such an applicationconcerns the isolation of macromolecules such as peptides, proteins,nucleic acid or other organic compounds. In such a case the use ofadsorptive particles is preferred. Most suitable particles will have, incombination with the porous matrix morphology, rapid adsorptionkinetics, a capacity and selectivity commensurate with the applicationand allows for desorption of the molecule with an appropriate agent. Theaffinity of suitable adsorptive particles for specific molecules can bedefined in terms of hydrophobic, hydrophilic or charged functionalities,in particular ion exchange functionalities, molecular (imprinted)recognition, epitope recognition, isomer selective or other specificinteractions. In an embodiment suitable adsorptive particulate materialis hydrophobic in nature.

In further embodiments the particulate material is functionalized forsize exclusion or for the separation of optically active compounds orthe separation of isomers or can be used in reversed phasechromatography. Separation of optically active compounds or theseparation of isomers may be based on selective affinity.

In another embodiment the particles are functionalised in order to serveas a component in a reaction mixture to promote reactivity in particularas catalyst. Also it may be desirable to combine adsorption andcatalysis. In particular the catalyst may be a biocatalyst.

Suitable adsorptive particles will be apparent to those skilled in theart and include cation exchange resins, union exchange resins, silicatype particles, for instance unmodified or derivatised with C₂, C₄, C₆,C₈ or C₁₈ or ion exchange functionalities, zeolites, ceramic particles,such as TiO₂, Al₂O₃, and the like, magnetic colloidal particles, porousor non-porous polymeric particles, such as porous polystyrene orstyrene-divinylbenzene type particles either unmodified or derivatisedwith for instance sulphonic acids, quaternary amines and the like,molecular imprinted particles and homogeneous) catalyst particles.

In a further embodiment the functional particle inside the porous matrixmay be altered in its function by a subsequent functionalisation.Ion-exchange particles may for example adsorb a protein which remains onthe particle by a subsequent crosslinking reaction. The protein modifiedion-exchange (IEX) particle now has a function different from itsoriginal adsorption function. For example, the protein modified IEXparticle may have now different adsorptive functionality or differentenantiomer separation. Another example is for instance theimmobilisation of a (homogeneous) catalyst on the functional particleinside the porous matrix.

The term particulate material as used herein is intended to encompassparticles having regular, in particular spherical or irregular shapes,as well as shards, fibres and powders, including metal powders, plasticpowders for instance powdered polystyrene, normal phase silica, fumedsilica and activated carbon.

Particles with an average particle (diameter) up to 100 μm may be used.It is preferred the average particle size is less than 50 μm and ispreferably in the range of 0.1 to 30 μm, preferably smaller than 20 μm.

The polymeric material may be a polymer including elastomers, acopolymer, mixture of polymers, mixture of copolymers or a mixture ofpolymers and copolymers. Examples of polymeric materials suitable foruse in the preparation of porous fibres according to the method of theinvention include polysulphone (PSF), polyethersulphone (PES), polyamide(PA), polyetherimide (PEI), polyimide (PI), polyethylene-co-vinylalcohol(EVAL), polyethylene-vinylacetate (EVAC), cellulose acetate (CA),cellulose triacetate (CTA), polyvinylidenefluoride (PVDF),polyvinylchloride (PVC) polyacrylonitrile (PAN), polyurethane (PUR)polyether ether ketone (PEEK) polyacrylicacid (PAA). However theinvention is not limited to those polymeric materials and other suitablematerials may be apparent to the skilled person. Also polymers havingmodifications, chemically and/or physically, may be used such as forinstance sulfonated polymers. Also mixtures of two or more polymers maybe used. In general it is advantageous to use polymers that arecompatible with components found in food products. Preferably suchpolymers demonstrates a low interaction with food components, this toprevent non-selective interactions, with components out of the feedstream.

Preferred polymeric materials are polyethersulphone, polysulfone,polyethylene-co-vinylalcohol, polyvinylidenefluoride an celluloseacetate.

In the method of the invention the polymeric material should bedissolved in a suitable solvent. The type of solvent depends on thechoice of the polymer. In view of the phase inversion process preferablysolvent are used that are well miscible with water. One or more solventscan be used together even in combination with nonsolvents. Suitablesolvents include, but are not limited to N-methyl-pyrrolidone (NMP),dimethyl acetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide(DMSO), formamide (FA), tetrahydrofurane (THF), ε-caprolactam,butyrolactone, in particular 4-butyrolactone, sulfolane, cyclohexanonsand triethylphosphate. Preferred solvents are NMP, DMAc, DMF, DMSO, THF,ε-caprolactam and 4-butyrolactone.

Water is the preferred coagulation medium. Other examples of possiblecoagulation media and non-solvents are methanol, ethanol, propanol,butanol, ethylene glycol, aceton, methyl ethyl ketone.

Intimately mixing the solvents the polymeric matrix material and theparticulate material provides the basic mixture that is to be extruded.

In order to obtain the desired porosity in the fibres mixtures ofnon-solvents and solvents in combination with variation in physicalprocess parameters like temperature, production rate, humidity, air gaplength, stretching and take up speed are used. Also for various reasonsadditives may be applied such as for instance to influence viscosity ofthe polymer solution, as pore former, as pore connectivity enhancer, toreduce or prevent macro-void formation and/or to introducehydrophilicity. Possible additives include, but are not limited topolyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyethyleneoxide(PEO), dextran, glycerol, diethylene glycol, (higher) alcohols such asoctanol, carboxylic acids or organic acids, such as oxalic acid, maleicacid, tartaric acid, fumaric acid, salts, such as LiCl and CaCl₂. It iswithin the competence of the skilled person to assess and apply suitable(mixtures) of (non-)solvents, additives and process conditions toproduce a fibre with desired properties.

For the production of fibres, either hollow, solid or solid supported,generally known extruders may be used. For instance by using adouble-walled cylindrical (tube-in-orifice) spinneret and applying abore liquid a hollow fibre is obtained. Not applying a bore liquidresults in the formation of a solid fibre. By spinning a thread or netwith the polymer a composite fibre can be obtained. Extrusion into awater bath results in solidification of the porous fibre havingparticulate material entrapped.

The matrix polymer concentration in the polymer solution is between 0.5and 50% by weight. The suitable amount of particles in the mixture thatis to be extruded depends on type of polymer and the concentration ofthe polymer that is used. In general the amount of particles in themixture that is to be extruded may vary between 1 and 95% by weight.Thus the mixture that is extruded comprises 0.5% to 50% by weightpolymeric material and 1% to 95% by weight of particulate material, theremainder being solvent. Additives and/or non-solvent can partly replacethe solvent and can vary between 0.01 and 50% by weight.

In an embodiment the matrix polymer concentration in the polymersolution is between 3 and 50% by weight and preferentially between 5-35%by weight. Preferably the matrix polymer concentration is less than 12%,more preferably less than 10% by weight. The preferred concentrationdepends on the specific polymer or polymers that are used, incombination with the specific particulate material and the desiredamount of particles in the fibre that is to be obtained.

In an embodiment the amount of particles in the mixture that is to beextruded varies between 1 and 60% by weight. Preferably the amount ofparticles in the mixture that is to be extruded is more than 5% byweight, being preferentially between 10 and 60% by weight. Thus themixture that is extruded comprises 3% to 50% by weight polymericmaterial and 1% to 60% by weight of particulate material, the remainderbeing solvent. Additives and/or nonsolvent can partly replace thesolvent and can vary between 0.01 and 50% by weight.

Furthermore, unexpectedly, it has been found that the size of theparticle, the functionality as well as the amount of particles in thepolymer solution have a distinct influence on the ultimate porestructure of the matrix. The smaller the particles the more spongy thematrix structure becomes. For instance it was observed that going from90 μm particles to 20 μm the structure changes form a macrovoidcontaining structure to a completely macrovoid free structure.Furthermore, the accessibility of the particles is significantlyimproved when the particle content increases. FIGS. 7 and 8 show thechange in porosity going from a fibre with 10% by weight of particulatematerial to a fibre with 75% by weight of particulate material.

In general it may be assumed that it is desired to have a polymericmatrix with as many particles as possible that are well accessible.However, it may also be assumed there is a balance between particle loadand accessibility, depending on a particular application of thepolymeric matrix. It may even be advantageous to use a polymeric matrixhaving macrovoids, which may be beneficial in view of convectivetransport and diffusional resistance in the polymeric matrix.

Thus in an aspect of the invention a method is provided for controllingporosity of a polymeric matrix having particulate material entrapped insaid matrix by varying the size of the particulate material. In yet afurther aspect a method is provided for controlling porosity of apolymeric matrix having particulate material entrapped in said matrix byvarying the content of the particulate material. In yet a further aspecta method is provided for controlling porosity in a polymeric matrixhaving particulate material entrapped in said matrix by varying thefunctionality of the particulate material. Varying functionality meanschemical groups in or on or of a particle.

The fibre that is prepared according to the method of the inventioncomprises 5-95% by weight of polymeric material and 5-95% by weight ofparticulate material, preferably 60-95% by weight of particulatematerial. Even at particle weight percentages of 75 and higher fibreshave been obtained with sufficient mechanical strengths. In anembodiment the fibre that is prepared according to the method of theinvention comprises 20-70% by weight of polymeric material and 30-80% byweight of particulate material, preferably 60-70% by weight ofparticulate material.

To produce fibres with desired porous properties a two-step phaseinversion process is used. Prior to entering a coagulation bath theexterior of the nascent fibre is in contact with a chosen mediaresulting in a change in composition of the exterior layer. This isconsidered as the first step of the phase separation process. When thefibre enters the coagulation bath the nascent fibre will further phaseseparate and the structure will be arrested. This is considered as thesecond step of the phase separation. In the first step the pore size andporosity of the outer wall of the fibre can be adjusted.

To influence the environment of the exterior of the polymer solutionleaving the die of the extruder, in a two stop phase inversion processin particular extrusion by means of a spinneret is used. Preferably aset-up is such in which a spinneret is used that allows for thecontrolled flow of a liquid, a vapor or a gas as an exterior medium ofthe fibre. Advantageously the two-step phase inversion process involvesthe use of a so-called triple layer spinneret as described in WO93/12868. The use of a triple layer spinneret is synonym for a two-stepphase inversion fiber formation process. A triple layer spinneret allowsfor the controlled flow of a liquid, a vapor or a gas an exterior mediumalong the fibre. For hollow fibers a bore liquid is applied through theneedle of the triple layer spinneret, which influences the inner surfacestructure. For the preparation of solid fibers the needle has nofunction and could even be missed.

The choice of the composition of the exterior medium in the triple layerspinneret and the contact time prior to entering the coagulation bathdetermine whether the exterior fibre surface becomes dense or porous.When the exterior is in contact with air of moderate humidity theexterior surface of the fibre turns out dense. To profit of optimalaccessibility of the entrapped particles a suitable medium should beflown along the exterior of the fibre during spinning. Preferably theexterior medium is a liquid mixture of solvent and nonsolvent for thepolymer. Preferably the nonsolvent is water. Alternatively it ispossible to apply a gas stream comprising a nonsolvent for the polymer.In this case preferably the nonsolvent is water vapor. A skilled personcan easily determine the desired amount of water vapor in the gas streamto produce a first phase inversion effect.

A two-step phase separation process, where the nascent fibre contactstwo different media consecutively, and which both influence the nascentfibre composition by interchange of solvent and nonsolvent, bypasses thetype of difficulties that relate to a one-step phase inversion processas disclosed in DD A 233,385, wherein the contact time with the firstmedium is short and the second medium is a strong coagualant for thenascent fibre composition. The two-step phase inversion process that isapplied according to the method of the present invention ensures thatthe particles in the porous matrix are well accessible and maintaintheir functionality after preparation.

A simple tube-in-orifice spinneret can also be used, but offers lessflexibility in altering the shell surface. Of course when solid fibresare produced the inner needle is no longer required and the triple layerspinneret is degraded to a tube-in-orifice spinneret, where the polymersolution is spun through the needle and the first coagulant through theorifice. In that case the dimensions of the tube and the orifice have tobe adjusted accordingly.

For additional enforcement of the fibre one or more thread wires, yarnsor the like of any material can be co-extruded with the fibre and beingentrapped in the core of the solid fibre or in the wall of the hollowfibre as essentially is described in WO 01/02095.

Typically the size of the pores in the fibre are not greater than 20 μm.Although the pore size is dependent on the application it should not belarger than the particle size to avoid particle loss during processing.

The optimum diameter of the fibre depends on the diffusion coefficientof the target particles, length of the adsorber and flow conditions.Typical fibre diameters are between 10 μm or 20 μm and 15 mm where as ismost cases it is beneficial to use fibres with diameters between 0.3 or0.5 and 3 mm.

The thus produced porous fibre may undergo post treatment such as forinstance heat treatment or further functionalisation steps to activatethe particle or to fix the porous structure of the fibre or to reducethe size of the pores of the porous fibre. Depending on polymer andparticles used, the skilled person will be able to determine a suitabletemperature or temperature range to apply in the heat treatment.

The invention further relates to a fibre obtainable by the methodaccording to the invention.

The fibres prepared according to the method of the invention can be usedas such, however, in another embodiment of the invention the fibres arecomprised in a module. Suitably such a module comprises spirally woundfiber mats packed inside a housing, a bundle of fibers packedlongitudinally inside a housing, transverse flow fiber configurationinside a housing, fibers wounded as a spool in parallel or cross-overmode inside a housing or any other orderly or disorderly fiber packingconfiguration inside a housing. Also other bodies comprising fibres,optionally in a finely divided form, prepared according to the method ofthe invention are within the scope of the invention. Such bodies includefor instance columns for chromatography.

The porous fibres and modules of porous fibres of the invention have awide variety of applications, depending upon the particle selection.They may be used for the adsorption and/or purification of compoundsfrom a reaction mixture or in fact from any compound mixture. Forexample, applications include peptide and protein isolation, immobilisedligands for affinity based separations, chromatography, immobilisedcatalysts and enzymes for reactions, release and product protection etc.Those skilled in the art will be able to choose the appropriateparticles and particle functionalisation in combination with appropriatepolymeric material and optionally additives depending upon the desiredapplication. Also a mixture of particles may be used.

A particular use of interest is the isolation of desired proteins fromfermentation broths, tissue broths, plant broths or cell broths ingeneral, catalytic and enzymatic reactions, detoxification, productprotection and release systems.

Example 1 Solid Fibre Polyethylene-Vinyl-Alcohol/Cation Exchange ResinStructure

A polyethylene-vinyl-alcohol (EVAL with 44% ethylene content) solidfiber was produced by dissolving 7 wt. % EVAL and 12 wt. %cation-exchange resin (CER) (Lewatit CNP 80 WS (Bayer), totalion-exchange capacity: 4.3 eq/l) and 7 wt. % octanol indimethylsulfoxide (DMSO). The resin particles were smaller than 20 μm.The obtained dispersion was extruded through a tube-in-orifice spinneret(OD=2.4 and ID=1.65 mm) into a water bath (20° C.), where phaseseparation occurred. There was no bore liquid used for the production ofsolid fibre. This way a porous solid fibre was obtained with a particleload of 60 wt. % CER, with 80% of the immobilised particles being activefor protein (BSA) adsorption. A BSA adsorption of 80 mg/g fibre has beenobtained.

Example 2 Hollow Fibre Polysulfone/Cation Exchange Resin Structure

A polysulfone hollow fibre was produced by dissolving 30 wt. %polysulfone (UDEL 3500) and mixing it with 30 wt. % of thestyrene-divinylbenzene type cation-exchange resin (CER) (AmberliteIR-120, total ion-exchange capacity: 4,4 meq/g-dry resin) inN-Methylpyrrolidone (NMP). The resin particles were smaller than 30 μm.This dispersion was extruded through a tube-in-orifice spinneret (OD=2.1and ID=1.0 mm) into a water bath (16-18° C.), where phase separationoccurred. The bore liquid consisted of 60% NMP and 40% water. Thespinning rate was 0.35 m/min. This way a porous hollow fibre wasobtained with a particle load of 50 wt. % CER, with 88% of theimmobilised particles being accessible for salt ions.

The produced hollow fibre without a post treatment shows a NaOH flux of7.9 mol·hr·m² and a Na₂SO₄ flux of 2.4 mol·hr·m². This results in arather low selectivity of 3.3. It appears that a heat treatment of theproduced fibres just above the glass transition temperature of thematrix polymer influences the fibres' properties considerably. A heattreatment of 10 minutes at 200° C. reduced the fluxes of NaOH and Na₂SO₄to values of 1 and 0.01 mol·hr·m², respectively. The NaOH/Na₂SO₄selectivity increased form 3.3 to 102.

Example 3 Solid Fibre Polyethylene-Vinyl-Alcohol/BSA-Modified CationExchange Resin Structure

A polyethylene-vinyl-alcohol (EVAL with 44% ethylene content) solidfibre was produced by dissolving 7 wt. % EVAL and 12 wt. %cation-exchange resin (CER) (Lewatit CNP 80 WS (Bayer), totalion-exchange capacity: 43 eq/l) and 7 wt. % octanol in dimethylsulfoxide(DMSO). The resin particles were smaller than 20 μm. The obtaineddispersion was extruded through a tube-in-orifice spinneret (OD=2.4 andID=1.65 mm) into a water bath (20° C.), where phase separation occurred.There was no bore liquid used for the production of solid fibre. Thisway a porous solid fibre was obtained with a particle load of 60 wt. %CER. The functional porous fibre was used for adsorption of bovine serumalbumin (BSA) in a batch experiment. The functional porous fibres havean adsorption capacity of 165 mg BSA/g fibre. The BSA-modifiedfunctional porous fibre was consecutively treated with a glutaraldehyde(GA) solution to chemically attach the protein into the porous matrix.The resulting solid fibre of polyethylene-vinyl-alcohol/BSA-modifiedcation exchange resin structure adsorbs bilirubin. It therefore has alsothe potential to adsorb other substances such as tryptophan,barbiturates or antidepressant.

Example 4 Solid FibrePolyethylene-Vinyl-Alcohol/Polyethyleneimine-Modified Zirconia ParticlesSelective for Endotoxins

A polyethylene-vinyl-alcohol (EVAL with 44% ethylene content) solidfibre was produced by dissolving 7 wt. % EVAL and 12 wt. % porouszirconia microspheres and 7 wt. % octanol in Dimethylsulfoxide (DMSO).The zirconia particles were smaller than 20 μm and can be eitherobtained commercially or synthesized tailored to the desired propertiesby polymerization-induced colloid aggregation. The obtained dispersionwas extruded through a tube-in-orifice spinneret (OD=2.4 and ID=1.65 mm)into a water bath (20° C.), where phase separation occurred. There wasno bore liquid used for the production of solid fibre. This way a poroussolid fibre was obtained with a particle load of 63 wt. % zirconia. Thefibre thus obtained was further treated to immobilize polyethyleneimine(PEI) onto the zirconia particles by coating it with a 2 wt. % PEIsolution in methanol. Crosslinking of the PEI by agents such as1,2-bis-(2-iodoethoxy)ethane or 1,10-diiododecane can influence thehydropholicity of the quaternized PEI. Such functional porous fibres ofpolyethylene-vinyl-alcohol/polyethyleneimine-modified zirconia particlesadsorb selectively endotoxins over proteins.

Example 5 Solid Fibre Polyethersulfone Cation Exchange Resin Structure

A polyethersulfone (PES) solid fibre was produced by dissolving 13.8 wt.% PES and 13.8 wt. % cation-exchange resin (CER) (Lewatit CNP 80 WS(Bayer), total ion-exchange capacity: 4.3 eq/l), 33.6 wt. % polyethyleneglycol (PEG 400) and 5.2 wt. % water in N-Methylpyrrolidone (NMP). Theresin particles were smaller than 20 μm. The obtained dispersion wasextruded through a triple layer spinneret (OD=2.4 and ID=1.65 mm) into awater bath (20° C.), where phase separation occurred. There was no boreliquid used for the production of the solid fibre. At the exterior ofthe nasecent fibre mixtures of NMP and water (first coagulant) wereflown. The contact time with the first coagulant was less than 1 second.This way a porous solid fibre was obtained with a particle load of 50wt. % CER. Scanning Electron Microscopy (SEM) pictures show clearly thatthe exterior surface is much denser when a first coagulant is used of 70wt. % NMP and 30 wt. % water compared to a mixture of 90 wt. % NMP and10 wt. % water, see FIGS. 5 and 6.

Example 6 Influence of Particle Content

To demonstrate the influence of particle content on the porosity ofpolymeric matrix fibres according to example 5 were prepared withvarying particle contents. FIG. 7 shows a fibre with a particle contentof 10% by weight in which clearly macrovoids are visible. FIG. 8 shows afibre with a particle content of 75% by weight in which is free ofmacrovoids.

1. Method for the preparation of a polymeric support matrix havingparticulate material entrapped in said support matrix in which thepolymeric support matrix is porous and the particles are well accessibleand maintain their functionality after preparation, said methodcomprising providing a mixture of polymeric material and particulatematerial in a solvent for the polymeric material and extruding saidmixture into a fibre and solidifying said fibre by a two-step phaseinversion process, wherein the two-step phase inversion processcomprises: (i) utilizing a spinneret to allow a controlled flow of aliquid mixture comprising a solvent and a non-solvent for said polymericmaterial, along an exterior medium of the nascent fibre, resulting in afirst phase separation of the exterior of the nascent fiber; and (ii)entering of said fiber into a coagulation bath, resulting in furtherphase separation and arrest of the structure of said fiber, to obtain ahollow or solid fiber containing about 60-95 wt % of particulatematerial.
 2. Method according to claim 1 in which the mixture that isextruded comprises 0.5% to 50% by weight polymeric material and 1% to95% by weight particulate material, the remainder being solvent. 3.Method according to claim 1 in which the solvent is selected from thegroup consisting of N-methyl-pyrrolidone (NMP), dimethyl acetamide(DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO),tetrahydrofurane (THF), ε-caprolactam and 4-butyrolactone.
 4. Methodaccording to claim 3 in which the solvent in the mixture of polymericmaterial and particulate material is replaced by 0.01-50% by weight ofone or more additives and/or non-solvents.
 5. Method according to claim4 in which the additives are selected from the group consisting ofoctanol, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), andglycerol.
 6. Method according to claim 1 in which the fibre comprisesabout 60-70% by weight of particulate material.
 7. Method according toclaim 1 in which the nonsolvent is water or water vapor.
 8. Methodaccording to claim 1 in which the spinneret is a triple layer spinneret.9. Method according to claim 1 in which the polymeric material isselected from the group consisting of polyethersulphone, polysulfone,polyethylene-co-vinylalcohol, polyvinylidenefluoride and celluloseacetate.
 10. Method according to claim 1 in which the particulatematerial in the porous matrix is altered in its function by a subsequentfunctionalisation.
 11. Method according to claim 1 in which theparticulate material is adsorptive particulate material.
 12. Methodaccording to claim 1 in which the adsorptive particulate material is anion exchange resin.
 13. Method according to claim 12 in which theadsorptive particulate material is hydrophobic in nature.
 14. Methodaccording to claim 1 in which the particulate material is used for sizeexclusion.
 15. Method according to claim 1 in which the particulatematerial is used for separation of isomeric compounds.
 16. Methodaccording to claim 1 in which the particulate material is used forseparation of optically active compounds.
 17. Method according to claim1 in which the particulate material is used in reversed phasechromatography.
 18. Method according to claim 1 in which the particulatematerial is functionalised, or is subsequently functionalised, with acatalyst or a biocatalyst.
 19. Method according to claim 1 in which theparticulate material is active carbon.
 20. Method according to claim 1in which for mechanical enforcement a thread, wire, or yarn isco-extruded with the fibre.
 21. Method according to claim 1 whichfurther comprises heat treatment.
 22. Method for controlling porosity ofa polymeric matrix having particulate material entrapped in said matrixby varying the size of the particulate material in the method accordingto claim
 1. 23. Method for controlling porosity of a polymeric matrixhaving particulate material entrapped in said matrix by varying thecontent by weight of the particulate material in the polymeric matrix inthe method according to claim
 1. 24. Method for controlling porosity ofa polymeric matrix having particulate material entrapped in said matrixby varying the functionality of the particulate material in the methodaccording to claim
 1. 25. Fibre obtained by the method according toclaim
 1. 26. Module comprising fibre according to claim 25, said modulecomprising a spirally wound fiber mat packed inside a housing, a bundleof fibers packed longitudinally inside, a housing, a transverse flowfiber configuration inside a housing, fibre wounded as a spool inparallel or cross-over mode inside a housing or an orderly or disorderlyfibre packing configuration inside a housing.
 27. Body comprising afibre, optionally in a finely divided form, according to claim
 25. 28. Amethod for the adsorption and/or purification of compounds from amixture of compounds or a reaction mixture comprising utilizing a fiberaccording to claim
 25. 29. A method for the immobilization of a catalystin a reaction mixture comprising utilizing a fiber according to claim25.
 30. A method for the immobilization of a chemical or biologicalcompound comprising utilizing a fiber according to claim
 25. 31. Themethod according to claim 28, wherein the mixture of compounds or thereaction mixture is a fermentation broth, a tissue broth, a plant brothor a cell broth.
 32. The method according to claim 1, wherein there isno additional step after (ii).